Creep resistant alloy



Oct. 30, 1962 C. G. BIEBER CREEP RESISTANT ALLOY Filed Feb. 1, 1960 1'86000! X SSEIELLS ATTORNEY 3,061,426 CREEP RESISTANT ALLOY Clarence G.Bieber, West Roselle Park, N.J., assignor to The International NickelCompany, Inc., New York, N.Y., a corporation of Delaware Filed Feb. 1,1960, Ser. No. 6,001 4 Claims. (Cl. 75-171) The present inventionrelates to strong heatand corrosion-resistant alloys and, moreparticularly, to strong, heatand corrosion-resistantnickel-chromium-cobalt alloys.

Heretofore, the art has endeavored to provide castable alloys which maybe subjected in use to temperatures in excess of about 1700 F. incorrosive atmospheres and which maintain adequate strength and ductilityunder these conditions. In order to be completely satisfactory, thealloys must not depend upon scarce or expensive elements in order toobtain the required strength at high temperatures. Although attemptswere made to overcome the foregoing difficulties and otherdisadvantages, none, as far as I am aware, was entirely successful whencarried into practice commercially on an industrial scale.

It has now been discovered that by the use of a specially coordinatedcombination of readily obtainable elements, it is possible to producealloys having substantially enhanced properties when exposed in use tohigh stresses at elevated temperatures of the order of about 1700 F. andhigher.

It is an object of the present invention to provide a novel alloy havingsubstantially enhanced characteristics at elevated temperatures andparticularly at temperatures in excess of about 1700 F.

Another object of the invention is to provide a novel heat-resistantarticle having substantially enhanced characteristics at temperatures inexcess of about 1700 F.

The invention also contemplates providing a novel turbine structurehaving substantially enhanced characteristics at temperatures in excessof about 1700" F.

It is a further object of the invention to provide a novel turbine bladehaving substantially enhanced characteristics at temperatures in excessof about 1700 F.

Other objects and advantages will become apparent from the followingdescription taken in conjunction with the accompanying drawing in whichthe FIGURE is a graph relating stress and a parameter commonly known asthe Larson-Miller parameter.

Generally speaking, the present invention contemplates novelnickel-chromiurn-cobalt alloys and articles, structures, etc., madetherefrom having substantially enhanced characteristics at elevatedtemperatures, and, particularly when subjected to temperatures in excessof about 1700 F comprising about 6% to about 12% chromium, about toabout 30% cobalt, about 1% to about 8% molybdenum, about 0.2% to about2% vanadium, about 4% to about 9% aluminum, about 0.5% to about 6.5%titanium, about 8% to about 12% aluminum plus titanium, about 0.001% toabout 0.1% boron, about 0.01% to about 0.25% zirconium, about 0.01% toabout 0.5% carbon, with the balance being essentially nickel. The termbalance essentially is used to include in addition to nickel in thebalance of the alloy, small amounts of impurities such as sulfur,phosphorous, etc., and incidental elements such as niobium, tantalum,manganese, silicon, copper, iron, etc., in amounts which do notadversely affect the novel advantageous characteristics of nitecl StatesPatent ice the alloy. The novel alloys of the present invention cancontain up to about 5% niobium, up to about 2% copper, up to about 1%silicon, up to about 2% manganese, up to about 0.2% calcium, up toabout4% tantalum and up to about 10% iron and more advantageously, up toabout 2% iron The alloys of the present invention exhibit excellentlives to rupture at elevated temperatures, for example, up to at leastabout hours lifewhen tested under a load of 35,000 pounds per-squareinch (p.s.i.) at 1700 F. in combination with a reasonable amount ofductility, for example, at least about 4% elongation under theaforestated conditions. The alloys can be used in the as-cast conditionbut can advantageously be treated by heating for about /2 to about 4hours at a temperature of about 2100 F. to about 2200 F. under an inertatmosphere such as helium, argon, etc. The alloys are then cooled ratherrapidly to a temperature below about 1700 F. while maintaining them inan inert atmosphere. The alloys and articles made therefrom may be agedin service or may be aged byheating for about 1 to about 20 hours attemperatures of about 1400 F. to about 1700 F. It is characteristic ofthe alloys of the present invention that they can be readily cast andthat they give excellent mold reproduction making them especially suitedfor use in the precision casting process. The alloys are usually meltedfrom either "a calculated charge or from remelt stock under an inertatmosphere (including vacuum) and are cast at temperatures between about2500 F. and about 3100 F. into molds preheated to about 1000 F. to about1800 F. If melted at atmospheric pressure a final treatment with calciumsilicide prior to casting is advantageous. When produced in this manner,alloys in accordance with the invention may be subjected in use underoxidizing conditions to temperatures up to about 2100 F.

In carrying the invention into practice, it is most advantageous tomaintain the composition of the novel alloys within the limited rangeset forth in Table I.

Table I Element Range, percent Chromium 8-12 Cobalt 10-20 Molybdenum 2-5Vanadium 0.25-1.50

Aluminum I 5-8 Titanium 1-6 Aluminum-l-titanium 9-1 1 Carbon 0.10.3Boron 0.005-0.05 Zirconium 0.05-0.1 Nickel Balance Alloys within thelimited range set forth in Table I exhibit lives to rupture in excess ofabout 100 hours when subjected to a load of 35,000 p.s.i. at 1700 F. andelongations in the range of about 3% to about 20% under the same testingconditions. It is advantageous to maintain a relationship between thevanadium and carbon contents of the alloys as set forth both broadly andin the more advantageous aspects in such fashion that the percentage ofvanadium is at least twice the percentage of carbon. Examples of alloycompositions within the scope of the present invention are set forth inTable II together with an outstanding composition selected from theprior art alloys.

Table 11 Per- Per- Per- Per- Per- Per- Per- Per- Per- Pen Per- Y N centcent cent cent cent cent cent cent cent cent cent Cr 00 Mo Al V 'Ii Cb 1C Zr Ni 1 10 15 3 5. 1 4. 5 0.18 0.02 0.05 Bal.

10 3 5. 5 1 5. 0 0. 18 O. 02 0.05 Bal.

12 15 2 5. 5 1 4. 5 0. 18 0. 02 0. 05 Del.

10 15 3 5. 5 1 5. 5 0.18 0.02 0.05 Bel.

10 15 3 5. 7 1 4. 5 0.18 0. 02 0. O5 Bal.

10 15 3 5. 5 0.5 5.0 0.18 0.02 0. 05 Bal.

12 5 6 0.6 0.12 0. O2 0. 50 Bal.

1 Including small incidental amounts of tantalum. 1 Including smallincidental amounts of manganese, sillicon, iron, etc.

Alloy No. A is representative of the best commercial alloys of the priorart. Alloys set forth in Table II were produced in various conditions asset forth in Table III and were stress-rupture tested under theconditions set forth in Table IV.

Table III Treatment designation Processing 1 treatment A.M. as cast.

V.M. as cast.

A.M. 2 hours at 2,150 F. V.M. 2 hours at 2,150 F.

A.M.=Melted at atmospheric pressure under argon. V.M.= Melted undervacuum.

The results of life-to-rupture tests conducted on alloys set forth inTable II which were heat treated as set forth in Table III and testedunder the conditions set forth in Table IV, are presented in Table V.Standard specimens having gage sections 0.250 inch in diameter and 1.0inch in length were used for these test purposes.

Table V Test condition Time to fracture, hours Elongation,

Processing t percen Alloy No. treatment WWW.

Hen- -er ws w es eprpr s crumqwumumoocncnow O It is characteristic ofthe alloys of the present invention that they exhibit, in addition tohigh strength at elevated temperatures, good resistance to thermalshock. When tested by repeatedly subjecting airfoil turbine bladesections to an intermittent heating and cooling cycle comprising heatingin a flame for one minute to 1800 F. and then cooling in air for oneminute, the alloys of the present invention withstand many thousandcycles without failure. For example, one alloy in accordance with thepresent invention withstood 5850 cycles prior to failure as indicated bythe formation of the first crack 0.125 inch in length. Under sameconditions prior art alloys in commercial use fail in one to twothousand cycles.

Referring now to the drawing, it is to be observed that the stressrupture characteristics of an alloy in accordance with the presentinvention containing about 10% chromium, 15% cobalt, 3% molybdenum, 5.5%aluminum, 5.0% titanium, 0.18% carbon, 0.02% boron, 0.05% zirconium, 1%vanadium and the balance cssentially nickel, which was heat treated at2150 F. for two hours and then air cooled, can be illustrated in themanner suggested by Larson and Miller (see Transactions of the A.S.M.E.,1952, volume 74, pages 765-771). It is to be noted that the figure showsa master curve for the aforementioned alloy obtained by plotting stressx1000 p.s.i. against P (parameter). Parameter P is obtained fromexperimental data by the use of the following formula whereinP=parameter,

T =absolute temperature in Rankine,

log t=common logarithm of the time to rupture in hours; and

C=a constant having a value of 25.

Table VI Rupture strengths, Temperature, F. p.s.i.

In addition to excellent rupture strengths the alloys of the presentinvention also exhibit excellent short-time tensile characteristics attemperatures ranging from room temperature up to and including 1800 F.Short-time tensile characteristics measured on the short-time hightemperature test scale for alloy No. 1 as set forth in Table II arepresented in Table VII.

T l VII 0.01% to about 0.25% zirconium, about 0.01% to about 0.5% carbonwith the balance being essentially nickel. Test mm 9 at 5933 r glongation, Reduction 2. An alloy for use as castings and characterizedby p r are S 152%,? percent 133; having a life to rupture of at leastabout 100 hours when 5 exposed at a temperature of 1700 F. to a load of35,000 Room temp 115,000 135,750 10.3 13.1 pounds per square inchcontaining about 8% to about 39%; igj 2: 31% "151; 12% chromium, about10% to about cobalt, about $882? 9 228 igg ggg Z 8 2% to about 5%molybdenum, about 9% to about 11% %:ggg:g 1331358 g8 10 aluminum plustitanium, about 5% to about 8% alu- 11000: 1011000 1211750 414 3:1minum, about 1% to about 6% titanium, about 0.25% to @885 g: 1358 52%?2:: 3:; about 1.50% vanadium, about 0.005 to about 0.05% boron, about0.05% to about 0.1% zirconium, about 0.1% Additional alloys inaccordance with the present invenr to about 03% Carbon With the balancebeing essentially tion are set forth in Table VIII. nickel.

Table VIII Alloy No. Percent Percent Percent Percent Percent PercentPercent Percent Percent Percent Or 00 Mo Al i V O B Zr Ni 3. 41 2. 995.95 5.05 0. 97 0.14 0.014 0.04 Bal. 14.54 3.00 6.10 5. 36 1.01 0.15 0.01s 0. 05 Bal. 8.8 3.13 6.00 5.5 0.97 0.15 0. 023 0. 05 Bal. 14.74 3.035.96 3.33 0.94 0.19 0.017 0.0 Bal.

1 Including small incidental amounts of silicon, manganese iron, etc.Each of the aforementioned alloys Nos. 10 to 13 which 3. An alloy foruse as castings and characterized by were vacuum melted and heat treatedat 215 0 F. for 2 having a life to rupture of at least about 100 hourswhen hours and then cooled, exhibited a 100 hour rupture life exposed ata temperature of 1700 F. to a load of 35,000 under the specificstress-temperature conditions as set forth pounds per square inchcontaining about 8% to about in Table IX. 12% chromium, about 10% toabout 20% cobalt, about Table IX 2% to about 5% molybdenum, about 9% toabout 11% aluminum plus titanium, about 5% to about 8% alu- Stress fo-100 minum, about 1% to about 6% titanium, about 0.25% Alloy 5 1 32?-fig rultllfe 35 to about 1.50% vanadium, about 0.005% to about 0.05%boron, about 0.05 to about 0.1% zirconium, about 0.1% m 1 900 14 000 toabout 0.3% carbon, with the balance being essentially 11 11900 131000nickel, the carbon and vanadium contents of said alloy g 838 2 888 40being so related that the vanadium percentage is at least twice thecarbon percentage. 4. An alloy for use as castings and characterized bya 'Idhe P lgllventlon pacrlnFularly i zg i g g z z prolonged life torupture when exposed at elevated temrotors etc. The novel alloys of thepresent invention oxldlzl-ng atmosphere contammg about 6% to about 12%chromium, about 5% to about 30% cobalt, about 1% to gay also be used asextruslon d1es, valves, valve seats, about 8% molybdenum, about 8% toabout 12% minum plus titanium, about 4% to about 9% aluminum, f gggggg gg f g gfi fjg if;$ 5233 about 0.5% to about 6.5% titanium, about 0.2% toabout stood that modifications and variationshnay be restored 5O 2%Vanadlum about F about 01% g about to without departing from the spiritand scope of the in- 001% to about 9 Zirconium t to 0 vention, as thoseskilled in the art will readily understand. carbon Wlth h balance bemg essentlany l Such modifications and variations are considered to be thecarbon and Vanad1 um contents of sald alloy bemg so within the purviewand Scope of the invention and related that the vanad1um percentage 1sat least twice the pended 1 j carbon percentage.

I claim: 1. An alloy for use as castings and characterized by aReferences Cited m the file of thls Patent prolonged life to rupturewhen exposed at elevated tem- UNITED STATES PATENTS p r t r to thecombmed e e of pp Stress and an 2,912,323 Bieber et a1 NW 10, 1959ox1d1z1ng atmosphere contammg about 6% to about 12% 920 956 b 1 J 121960 chromium, about 5% to about 30% cobalt, about 1% to Is at et about8% molybdenum, about 8% to about 12% alu- OTHER REFERENCES mmum plust1tan1um, about 4% to about 9% alummum, about 0.5% to about 6.5%titanium, about 0.2% to about Journal Of Metals, VOL September 1953(Nisbet 1:) 2% vanadium, about 0.001% to about 0.1% boron, about (pages1149-1165 relied upon).

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,061,426 October 30, 1962 Clarence G. Bieber It is hereby certifiedthat error appears in the above numbered patent requiring correction andthat the said Letters Patent should read as corrected below.

Columns 3 and 4, Table II, eleventh column, line 10 thereof,- for 0.50"read 0.05 columns 5 and 6, Table VIII, tenth column, line 3 thereof, for"0.05" read 0.04

Signed and sealed this 21st. day of May 1963,,

(SEAL) Attest:

ERNEST w. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents

1. AN ALLOY FOR USE AS CASTINGS AND CHARACTERIZED BY A PROLONGED LIFE TORUPTURE WHEN EXPOSED AT ELEVATED TEMPERATURES TO THE COMBINED EFFECTS OFAPPLIED STRESS AND AN OXIDIZING ATMOSPHERE CONTAINING ABOUT 6% TO ABOUT12%% CHROMIUM, ABOUT 5% TO ABOUT 30% COBALT, ABOUT 1% TO ABOUT 8%MOLYBDENUM, ABOUT 8% TO ABOUT 12% ALUMINUM PLUS TITANIUM, ABOUT 4% TOABOUT 9% ALUMINUM, ABOUT 0.5% TO ABOUT 6.5% TITANIUM, ABOUT 0.2% TOABOUT 2% VANADIUM, ABOUT 0.001% TO ABOUT 0.1% BORON, ABOUT 0.01% TOABOUT 0.25% ZIRCONIUM, ABOUT 0.01% TO ABOUT 0.5% CARBON WITH THE BALANCEBEING ESSENTIALLY NICKEL.